I'm sorry that your question wasn't answered in a timely manner. We don't have many avian vets on this site. Can you upload a photo(s) of this chicken's head to our conversation? You can use the paperclip icon in the toolbar above your message box (if you can see that icon) or you can use an external app such as dropbox.com/ I can be more accurate for you if I can see what you're seeing.

Birds don't have a temperomandibular joint that could dislocate. I suspect that you're seeing congenital scissor beak or prognathism, acquired prognathism, or perhaps a deviated maxilla due to trauma.